SI AND POTASSIUM ELEMENT FREE

However, pioneering analyses by Humayun and Clayton 9 on a wide variety of planetary materials yielded indistinguishable 41K/ 39K ratios within ☐.5‰, which is inconsistent with significant isotope fractionation predicted by free evaporation. This extensive depletion has motivated the search for K isotope fractionation associated with evaporation. Potassium is among the most abundant MVEs, and K/U ratios measured in meteorites provide a convenient assessment of the relative depletion of MVEs to refractory elements in their parent bodies 6, 7, 8.Ĭompared with CI chondrites, K is highly depleted in terrestrial bodies, with the Moon and Vesta showing similarly high levels of depletion (~ 95%), followed by Earth (86%) and Mars (76%) 6, 7, 8. Here we use stable K isotopes to study volatile depletion processes in planetary bodies.

Studies of moderately volatile elements (MVEs) have provided valuable insights to distinguish between these scenarios because their isotopes are fractionated to different extents and/or in different directions during these processes. This depletion has been debated to reflect either 1) devolatilization of interstellar dust and inheritance of the depletion by the inner solar nebula 1, 2) incomplete condensation from the dispersing solar nebula 2, 3) accretion of volatile-depleted materials like chondrules 3, 4, or 4) evaporative loss during planetary accretion or degassing 5, 6, 7.

The inner Solar System, which features terrestrial planets, the Moon, and the asteroid belt, is depleted in volatile elements relative to the bulk solar composition sampled by carbonaceous Ivuna-type (CI) chondrites. Furthermore, nebula-wide K isotopic variations primarily reflect volatility-driven fractionations instead of presolar nucleosynthetic heterogeneity proposed previously.Ĭondensation and evaporation play a central role in shaping the volatile inventory of planets and their potential for harboring life. Therefore, the APB may provide a rare example of isotope fractionation controlled by condensation, rather than evaporation, at a planetary scale. In contrast with the isotopically heavy Moon and Vesta, we find that angrites are strikingly depleted in the heavier K isotopes, which is best explained by partial recondensation of vaporized K following extensive evaporation on the angrite parent body (APB) during magma-ocean stage. Here, we leverage improved sensitivity and precision of K isotopic analysis to constrain the mechanism of extreme K depletion (>99.8%) in angrites. They are prime targets for investigating the formation of volatile-poor rocky planets, yet their exceptionally low volatile content presents a major analytical challenge. Angrite meteorites sample the most volatile-depleted planetesimal in the Solar System, particularly for the alkali elements. Volatiles are vital ingredients for a habitable planet.

Si and potassium element